WASHINGTON — Nearly a year after the Boston Marathon bombing — and just weeks before the next race — multiple security investigations remain bogged down, leaving unanswered questions about missed signals and communication breakdowns.

Members of Congress and former security officials are growing impatient over what they consider the slow pace of Washington’s official reviews of how the Tsarnaev brothers avoided scrutiny in the runup to last year’s Marathon.

“The delay is unconscionable,” said Tom Ridge, who dealt with the aftermath of the Sept. 11, 2001, attacks as
secretary of Homeland Security.

“If there was miscommunication or failure to communicate, man up,” added Ridge, now a homeland security consultant. “The tragedy was bad enough. To fail to accept there may have been some procedures that were flawed — you want to correct that to make sure you avoid a similar incident in Boston or elsewhere.”

Multiple investigations were launched last year in Congress and in Washington’s security establishment to review how officials handled information about the potential radicalization of one of the brothers and whether that information was appropriately shared among agencies.

Jewel Samad/AFP/Getty Images/File

Former Homeland Security Secretary Tom Ridge decries the delays.

The reviews also are intended to determine what steps may be necessary to help prevent a similar attack.

But there has been little public accounting for what may have gone wrong. The delays, according to members of Congress, aides, and former security officials, are the result of foot-dragging by several agencies, including the Department of Homeland Security and the Federal Bureau of Investigations.

‘There are too many unanswered questions about how the Tsarnaev brothers were able to carry out the attack.’

Senator Kelly Ayotte, Republican of New Hampshire

The absence of the reports has led to calls for releasing more information into the public arena before the April 15 anniversary of the bombing. Only one group, the House Committee on Homeland Security, has pledged to complete its review by then.

“It’s been too long,” said Representative Bill Keating, a Bourne Democrat and member of the committee. “The urgency is quite obvious: There’s the threat of future attacks.”

The committee’s review was expected to be released before the end of January, but it has remained under review by a number of officials, Keating said.

Senator Kelly Ayotte, a New Hampshire Republican, asked Department of Homeland Security officials during a budget hearing on Thursday why answers were not coming faster.

“Nearly a year after the Boston Marathon bombings, I’m concerned that there are too many unanswered questions about how the Tsarnaev brothers were able to carry out the attack,” Ayotte said in a statement to the Globe.

Ayotte, along with Senator Tom Coburn, an Oklahoma Republican, sent a letter last month asking the Department of Homeland Security why they had not yet provided a long-promised report on lessons learned. John Cohen, the department’s principal deputy counterterrorism coordinator, told committee staff during a briefing in June — nearly nine months ago — that it would be ready “in a few weeks,” the senators wrote.

“We’re almost done,” Jeh Johnson, the secretary of Homeland Security, said during the Senate hearing on Thursday, without explaining the delays. “We need to do a little more scrubbing, and we will get it to you in the short term.”

Senator Elizabeth Warren, Democrat of Massachusetts, called on federal agencies to expedite their reviews.

“I appreciate that the pending federal reports must be thorough and comprehensive,” she said. “But nearly a year later ... [agencies] must expedite their reviews and release those findings publicly so that Boston and other communities across the country can take additional steps to improve their security measures.”

Senator Edward J. Markey did not respond to requests for comment on the delays.

Even if the reports find there were no intelligence failures, they could provide insights into how the government should respond to so-called “lone wolves,’’ such as Tamerlan and Dzhokhar Tsarnaev of Cambridge, who authorities say cooked up the Boston Marathon bomb plot outside of any formal terror network.

The bombings killed three people and injured more than 260. Tamerlan Tsarnaev was killed in a shootout with police 3½ days after the bombing; Dzhokhar was captured in Watertown and is awaiting trial on 30 charges in federal court.

There had been early signs, in the forms of Russian warnings to US security officials, that Tamerlan Tsarnaev was under the influence of radical Muslim ideas. There also have been questions about whether the FBI should have more directly alerted law enforcement officials in Massachusetts about Tamerlan’s potential radicalization, particularly after he traveled to the Russian province of Dagestan in 2012.

“We have to be very tough, tougher than might seem fair to the folks at the FBI, in analyzing what happened at the Marathon last year,” said former US senator Joseph Lieberman of Connecticut, who helped establish the homeland security department after the Sept. 11 attacks.

“Here was a case where information that the feds had was not shared with state and local law enforcement. The question is why,” Lieberman said. “We don’t know exactly what state and local police would have done with that. But my guess is further surveillance and questioning of the Tsarnaevs. And that could have prevented this from happening.’’

In addition to the House Homeland Security report and the Department of Homeland Security review, a third major review is being conducted at the request of James R. Clapper, the director of national intelligence.

That report is expected in the “early spring” and will contain input from the CIA, Justice Department, and the Department of Homeland Security.

It will be a classified report, and some close observers expect the unclassified summary of the findings to be fairly limited.

“The inspectors general review team has collected data, conducted interviews, and performed analysis in order to examine the information available to the US government before the bombings,” Intelligence Community Inspector General I. Charles McCullough III, who is leading the review, said in a statement to the Globe. “The team is also studying the information-sharing protocols and procedures followed between and among intelligence and law enforcement agencies.”

In some corridors of Congress, there is an increasing sense that all of the reports are overdue.

“We would have failed at our jobs if there isn’t a public reckoning of what happened before the anniversary,” said one top Senate aide, who asked not to be identified because he was not authorized to speak publicly. “Hope like hell everyone gets their work done.”

One of the difficulties, congressional members and aides say, is that the FBI has been uncooperative. They have declined several offers to testify, in public or in a classified setting.

Congressional committees could have issued subpoenas to force the FBI to testify but have not taken that step. In declining to testify, the FBI previously has cited the ongoing criminal case against Dzhokhar Tsarnaev.

The FBI said it has “fully cooperated’’ with congressional committees but did not comment further.

Keating said the FBI was given three opportunities to testify before the House Committee on Homeland Security.

“There hasn’t been full cooperation,” Keating said. “Two trips to Russia and I get more information than I do going down the street 10 blocks in Washington.”

A hearing scheduled by the Homeland Security Committee that had been scheduled to be held in Boston will now be held in Washington after Mayor Martin Walsh said such a high-profile event before the anniversary could be a distraction, officials said.

In addition to the federal reviews, officials in Massachusetts have been planning their own accounting of the Marathon bombing. The report, which has involved hundreds of interviews, is meant to address both the security preparations for the Marathon as well as the response to the bombing.

It generally does not touch on the intelligence sharing, which the federal reports are reviewing, or the investigation.

The state report, which is being conducted by TriData, a division of Virginia-based System Planning Corp that has done reviews of other mass tragedies such as the shootings at Virginia Tech, was expected by March 1 but also has been delayed as the scope of the report has ballooned.

“We are disappointed that the report is not final and released,” said Kurt Schwartz, the Massachusetts undersecretary for Homeland Security and Emergency Management.

State agencies are reviewing draft reports, Schwartz said, and changes have been incorporated into planning for next month’s Marathon.

“I’m not going to talk about in detail of what we’re doing differently, but I can say the operational plan to do pre-event intelligence analysis is just far more comprehensive going into the 2014 Marathon than it was going in the 2013 Marathon,” Schwartz said. “A lot of work has gone into ensuring that databases are scrubbed for new information and old information — that dots are being connected across databases, local, federal, and international.”

Bryan Bender and Tracy Jan of the Globe staff contributed to this report. Matt Viser can be reached at matt.viser@globe.com.